Method using low friction loss liquid composition having resistance to shear degradation

ABSTRACT

A method of reducing the shear degradation when pumping through conduits, such as well tubing during hydraulic fracturing operations and pipelines, a liquid containing a friction loss reducing additive comprising adding to the liquid the friction loss reducing additive at least partially in chunk or granular form so that the additive is present at least partially in chunk or granular form when the mixture is passed through the pump.

United States Patent 91 McClaflin et al.

[451 May 1, 1973 METHOD USING LOW FRICTION LOSS LIQUID COMPOSITIONHAVING RESISTANCE TO SHEAR DEGRADATION [75] Inventors: Gifford G.McClaflin; Dennis J.

Royer, both of Ponca City, Okla.

[73] Assignee: Continental Oil Company, Ponca City, Okla.

[22] Filed: Feb. 16, 1971 [21] Appl. N01: 115,867

Root 166/308 3,351,079 11/1967 Gibson ..137/13 3,375,872 4/1968McLaughlin et al.. ..166/308 UX 3,434,485 3/1969 Lummus .1. ..137/133,483,121 12/1969 Jordan ..166/308 X 3,520,313 7/1970 Seymour ..166/308X. 3,542,044 11/1970 Hansen .....l66/308 X 3,559,664 2/1971 Seymour252/8551? Primary Examiner-Stephen J. Novosad v Att0rney--Joseph C.Kotarski, Henry H. Huth, Robert B. Coleman, Jr. and Gerald L Floyd [5 7ABSTRACT A method of reducing the shear degradation when pumping throughconduits, such as well tubing during hydraulic fracturing operations andpipelines, a liquid containing a friction loss reducing additivecomprising adding to the liquid the friction loss reducing additive atleast partially in chunk or granular form so that the additive ispresent at least partially in chunk or granular form when the mixture ispassed through the pump.

5 Claims, No Drawings polyacrylamide,

METHOD USING LOW FRICTION LOSS LIQUID COMPOSITION HAVING RESISTANCE TOSHEAR DEGRADATION Background of the Invention l. Field of the Invention1 The present invention relates to liquid compositions having reducedfriction loss when passed through conduits. More particularly theinvention concerns such compositions having decreased shear degradation.

2. Description of the Prior Art Energy must be supplied to move a liquidfrom one location to another via a conduit or pipe. When a liquid ispumped through a conduit a pressure is developed on the positive ordischarge side of the pump. The pressure in the conduit immediatelyadjacent the discharge side of the pump will be greater than thepressure farther along the conduit away from the pump. This differencein pressure, often referred to as the pressure drop, friction loss, or.drag, is generally more pronounced the faster the liquid flows. In manyindustrial operations where a large volume of liquid is moved rapidly,such as in the hydraulic fracturing of subterranean formationspenetrated by a well and the transportation of liquids long distancesthrough pipelines, a large amount of energy is expended in moving theliquid. If the pressure drop could be reduced, either larger volumes ofliquid could be moved with the same pump capacity or the pressure and/orenergy requirements for moving a given liquid volume reduced. Additivesare known which reduce the friction loss or drag of liquids flowingthrough pipes. For aqueous base liquids such additives include gums suchas guar gum, hydroxy-ethyl cellulose, polyethylene oxide, polyethyleneoxide, hydrolyzed polyacrylamide and copolymers of acrylamide andmethylenebisacrylamide. For oil base liquids such additives includepolymers such as polyisobutylene and copolymers of ethylene and a highermolecular weight alpha olefin.

Generally these additives are added to the base liquid as finelyparticulated solids which readily dissolve or disperse in the liquid.Alternatively, the additives are first added to some solvent to form aconcentrated solution of the additive which readily dissolves in thebase liquid.

Many friction loss control additives work well as long as they are notsubjected to excessive shear. Mere passage of the liquid through aconduit, even at a high flow rate so that the fluid is in turbulentflow, is not particularly determental. However in flowing liquidsthrough conduits it is necessary to provide some means of moving theliquids. Thus the liquids are passed through pumps. If the conduit is anelongated one, such as a pipeline, the liquid may pass through aplurality of pumps between its point of origin and its destination. It Ihas been the experience that friction loss control additives tend todegrade, i.e. partially lose their effectiveness, when exposed to shearstress, such as passing through a pump. The reason for this degradationis not entirely clear, but it has been postulated that the friction losscontrol additives exist in the liquid as long chain aggregates which arebroken up by the shearing action of a pump. This altered additive isgenerally less effective in controlling friction loss than the originalmaterial.

It is an object of this invention to provide a liquid composition havingreduced friction loss when passed through conduits, which compositionhas decreased shear degradation. It is another object to provide such aliquid composition which can be passed through a pump without excessiveshear degradation. It is a further object to provide a low friction lossliquid which retains a substantial portion of its low friction lossproperties when passed through a pump. It is a still further object toprovide such a composition for use in pipelines. Other objects,advantages and features will become apparent from the followingdescription and appended claims.

BRIEF SUMMARY OF THE INVENTION control additive for such liquid suchfriction loss con- I trol additive being present at least partially inchunk or granular form.

DESCRIPTION OF THE PREFERRED EMBODIMENT The liquids which aretransported or transmitted through the conduit may be eitheraqueous-based or oil-based. Examples of aqueous-based liquids includewater, brine, gels, acid solutions and the like. Examples of oil-basedliquids include oleaginous or petroliferous liquids as well asemulsions, suspensions and dispersions thereof, more particularly crudeoil, refined petroleum products such as kerosene,.pale oil, diesel oil,fuel oil and asphalt and derivatives of such petroleum products. Wherethe liquid is a hydraulic fracturing fluid for subterranean wellformations, such liquid may also contain solid particulate matter inertto the system, such as sand, as a propping agent, a fluid loss controladditive and other materials commonly added to fracturing fluids. Wherethe liquid is being transported from a point of origin to somedestination through a pipeline, the liquid may contain solids inert tothe system such as coal or ore which is being transported.

The known friction reducing agents are generally solids which aresoluble, often slowly soluble, in the liquid being transported. One ofthe problems recog- The problem confronting the instant inventors was adecrease in effectiveness of the friction reducing additure was thenpumped through a conduit at high flow rate. It was found that in such asystem the portion of the friction reducing agent added in chunk formretained its effectiveness after having passed through the pump. Oneexplanation of this phenomenon is that the slowly-dissolving frictionreducing agent passes through the pump at least partially in chunks orgranules. Then downstream of the pump these chunks or granules continueto dissolve or disperse supplying the liquid with non-degraded frictionreducing additive.

The following friction reducing additives were used as examples oftypical species:

FRA-l (for use in oil) Polyisobutylene having a weight average molecularweight of 5.2 10

FRA-2 (for use in oil) Copolymer of ethylene and propylene containing 49mole percent ethylene having a reduced specific viscosity, 0.2 gram in100 ml decalin at 135C of 16.2, and a molecular weight estimated fromthe reduced specific viscosity of more than 10.

FRA-3 (for use in aqueous media) Polyacrylamide polymer 30% hydrolyzedby reaction with sodium hydroxide and having a molecular weight suchthat a 0.5 weight percent solution of the polymer in a 4 weight percentaqueous sodium chloride solution has a viscosity measured on an Ostwaldviscometer of 35 centipoises at 25C.

FRA-4 (for use in aqueous media) Guar gum.

A pipe viscometer apparatus was used to determine the effect on frictionloss of the form in which friction reducing additives are added toliquid media. This apparatus consisted of a 20 foot long section of0.305 inch inside diameter tubing. The tubing was in the form of a nearloop so that both ends thereof could be positioned in a 5 gallon bucket.A 1 /2 horsepower lngersoll- Rand 3,455 rpm, it MCS size, 20 gallon perminute centrifugal pump was positioned in the tubing near one end of thetest loop. A first pressure gauge ranging from 30 ounces per square inchto 30 pounds per square inch pressure was positioned along the tubingfive feet from the discharge end of the pump. A second similar pressuregauge was positioned feet farther downstream from the first pressuregauge. Four gallons liquid medium plus a minor amount of frictionreducing additive was used. A flow rate of approximately 7 gallons perminute was established through the apparatus. A velocity of 30.5 feetper second and a Reynolds number of approximately 20,000 resulted whendiesel oil was used as the liquid medium. Measurements were carried outby adding 4 gallons liquid media to the 5 gallon bucket, starting thepump to circulate the same through the tubing, observing the differencein pressure (pressure drop) as shown on the two gauges, adding afriction reducing additive to the 5 gallon bucket and again observingthe pressure drop. The percent friction reduction is calculated asfollows:

Percent friction reduction (pressure drop of liquid medium) (pressuredrop of friction reducing additive solution) ditive. The results showthat when the friction reduction additive is added in particulate formthe friction reduction is initially slightly lower than when theadditive is first dissolved in some solvent prior to being added to thetest solution. However when the additive is used in particulate form arelatively high proportion of the friction reduction is retained afterseveral passes through .a pump whereas test solutions containing thepre-dissolved additive showed sharply reduced friction reduction uponsimilar treatment. Thus use of the additive in particulate form ishighly advantageous.

Friction Number reduction of Friction additive Liquid passes reducconc.media through tion (weight which used Added as pump 0.1 FRA-l Diesel Oil10% solution in l 45 diesel oil 0.1 FRA-l Diesel Oil 10% solution in 5 7diesel oil 0.l FRA-l Diesel Oil 20 mesh* particles 1 40 0.1 FRA-l DieselOil 20 mesh* particles 5 32 0.1 FRA-Z Diesel Oil 10% solution in 1 53diesel oil 0.1 FRA-Z Diesel Oil 10% solution in 5 9 diesel oil 0.1 FRA-ZDiesel Oil 20 mesh* particles 1 50 0.1 FRA-Z Diesel Oil 20 mesh*particles 5 39 0.1 FRA-3 Water 10% solution 1 in water 0.1 FRA-3 Water10% solution 5 4 in water 0.1 FRA-3 Water 20 mesh* particles 1 33 0.1FRA-3 Water 20 mesh* particles 5 25 0.1 FRA-4 Water 10% solution I 67 inwater 0.1 FRA-4 Water 10% solution 5 1 1 in water 0.1 FRA-4 Water 20mesh* particles 1 55 0.1 FRA-4 Water 20 mesh* particles 5 42 (pressuredrop of liquid medium) Measurements were made after the test fluid hadpassed through the centrifugal pump'one time and *U.S. Standard SeiveSeries.

The particle size in which the friction reducing additive is useddepends on its rate of solubility in the liquid to which it is added.The lower limit is the minimum size which will still be present inparticulate form when the system passes through the first pumpdownstream of the point of introducing the additive. Thus particles willpass through the pump and continue to dissolve downstream thereof. Theupper limit is governed by economics and the ability of the pump tohandle large particles.

Broadly the particles size can range from 5 to 300 mesh, US. StandardSeive Series. It is difficult for many pumps to handle solutionscontaining particles larger than about 5 mesh. If less than 300 meshparticles are employed, even of additives which are relatively slowlysoluble in the liquid medium, the decrease in friction loss reduction isstill pronounced upon passing through a pump. A preferred particle sizerange is from 10 to mesh.

When using the friction reducing additive in particulate form, theremust be an effective amount of additive dissolved or intimatelydispersed in a liquid friction reducing-form throughout the time periodof transportation of the base fluid being pumped through the conduit.When this time period is extended, such as in a long pipeline, it isoften convenient to use the friction reducing additive in a varyingparticle size range. Thus the smaller particles tend to dissolve ordisperse more rapidly providing friction reducing properties immediatelyafter mixing the friction reducing additive and the base fluid. Thelarger particles tend to dissolve slowly and disperse completely at alater time providing friction reducing properties for at a substantialtime after mixing. Thus a more or less even release of additive to thebase fluid is achieved throughout the time period of transportation. Apreferred friction reducing additive of varying particle size is onehaving at least percent (by weight) of the particles with a size rangeof from 5 to mesh, at least 20 percent of the particles with a sizerange of from to 90 mesh and at least 20 percent of the particles with asize range of from 100 to 200 mesh. The remaining percentage necessaryto constitute 100 percent may be of any particle size within the rangeoffrom 5 to 300 mesh.

We claim:

-1. In the process of passing at a high flow rate through a pump in atransportation system comprising one or more pumps and one or moreconduits connected thereto of a mixture of a liquid and a friction lossreducing additive, which is slowlysoluble in said liquid, theimprovement of maintaining the friction loss reducing additive at leastpartially in the form of solid particles having a size range of from 5to 300 mesh-duringthe passage of said mixture through the pump to cleshave a size range of from 5 to 300 mesh.

3. The process of claim l wherein the conduit comprises a pipeline. I

4. The process of claim 1 wherein the conduit comprises oil well tubing.

'5. In the process of hydraulically fracturing an earth formationpenetrated by a well wherein a liquid fracturing fluid is passed througha pump, down the well and into the earth formation at a high velocity tofracture the earth formation, the improvement of decreasing the 20friction loss in the flow of the liquid fracturing fluid which comprisespassing through the pump a mixture of a liquid fracturing fluid and afriction loss reducing additive which is slowly soluble in said' liquidand at least partially in the form of solid particles having a sizerange of from 5 to 300 mesh during the passage of said mixture throughthe pump to reduce the shear degradation of said friction loss reducingadditive.

2. The process of claim 1 wherein the friction reducing agent isutilized in a varying particle size in the range wherein at least 20percent by weight of the particles have a size range of from 5 to 30mesh, at least 20 percent of the particles have a size range of from 40to 90 mesh, at least 20 percent of the particles have a size range offrom 100 to 200 mesh and the remaining particles have a size range offrom 5 to 300 mesh.
 3. The process of claim 1 wherein the conduitcomprises a pipeline.
 4. The process of claim 1 wherein the conduitcomprises oil well tubing.
 5. In the process of hydraulically fracturingan earth formation penetrated by a well wherein a liquid fracturingfluid is passed through a pump, down the well and into the earthformation at a high velocity to fracture the earth formation, theimprovement of decreasing the friction loss in the flow of the liquidfracturing fluid which comprises passing through the pump a mixture of aliquid fracturing fluid and a friction loss reducing additive which isslowly soluble in said liquid and at least partially in the form ofsolid particles having a size range of from 5 to 300 mesh during thepassage of said mixture through the pump to reduce the shear degradationof said friction loss reducing additive.